A sanitary washing apparatus for washing the private part of the human body comprises a heating device that adjusts the temperature of washing water for use in washing to an appropriate temperature in order not to give an unpleasant feeling to the human body. Examples of the heating device principally include a hot water storage type sanitary washing apparatus and an instantaneous heating type sanitary washing apparatus.
The hot water storage type sanitary washing apparatus comprises a hot water tank that stores a predetermined amount of washing water beforehand while heating the washing water to a predetermined temperature with a built-in heater. In washing the private part of the human body, a method is employed in which the washing water heated to the predetermined temperature beforehand in the hot water tank is fed to a nozzle from which the washing water is sprayed, using the tap water pressure or by a pump or the like.
In the hot water storage type sanitary washing apparatus, the washing water in the hot water tank has to be continuously kept at the predetermined temperature beforehand until the time of washing the private part of the human body. This requires power to be continuously supplied to the heating device, resulting in increased power consumption. In addition, when a plurality of persons successively wash their private parts to use up more than the amount of washing water that is heated beforehand to the predetermined temperature in the hot water tank, the temperature of the washing water in the hot water tank decreases below the predetermined temperature to give an unpleasant feeling to the human bodies.
On the other hand, the instantaneous heating type sanitary washing apparatus comprises a heating device that is quick at increasing the temperature of washing water, such as a ceramic heater. In washing the private part of the human body, a method is employed in which the washing water is instantaneously heated to a predetermined temperature by the heating device, and fed to a nozzle from which the washing water is sprayed, using the tap water pressure or a pump or the like.
In the instantaneous heating type sanitary washing apparatus, therefore, the washing water does not have to be continuously kept at the predetermined temperature beforehand. Power supply to the heating device is necessary only during the use, which results in reduced power consumption. Moreover, even if a large amount of washing water is used for washing the private parts of the human bodies by, e.g., long-time washing or continuous use of the toilet, the temperature of the washing water can be prevented from decreasing below the predetermined temperature to give an unpleasant feeling to the human bodies (refer to JP 10-160249 A).
A heating device typically has a configuration in which a heating element is held in a case body. When this heating device is used to instantaneously heat washing water, the heating device thermally expands instantaneously, and contracts after the heating is completed. This causes a great stress to be instantaneously applied to the case body. As a result, the heating element or the case body may be damaged or deform.